U.S. Pat. No. 4,332,291 describes a heat exchanger comprising a series of conduits arranged adjacent each other but spaced apart, their external surfaces being formed with registering grooves. A set of fin elements in the form of transversely slotted metal strips is arranged in a stack between adjacent conduits with the longitudinal edges of each fin element extending into registering grooves in the opposed conduit surfaces. Each fin element has a central longitudinal zone, a transverse end zone at each end and two substantially planar longitudinal edge zones, the central longitudinal zone being planar and the edge zones each defining an obtuse included angle with the plane of the central longitudinal zone. Both edge zones lie on the same side of the plane of the central longitudinal zone.
In order for these fin elements to perform efficiently, this earlier patent describes fin elements having at one end a relatively wide transverse end zone and at the other end a relatively narrow transverse end zone. Alternate fin elements are displaced in the stack so that the slots in each fin are staggered relatively to those in its immediate neighbours but aligned with the slots in similarly positioned fin elements.
In the heat exchanger of U.S. Pat. No. 4,332,291, the creation of the slots from metal strip leads to a wastage of material since the metal stamped out of the slots is discarded. Also, the staggered pattern of alternate fin elements required for efficient heat exchange requires that the end zones of the fin elements must be distinguished and the elements correctly oriented during assembly. This adds to the already substantial labour costs inherent in assembling this type of heat exchanger.
U.S. Pat. No. 2,703,226 describes a heat exchanger with fin elements in the form of a U-shaped channel which is slit transversely at intervals along its length in its central longitudinal zone to provide a series of fins, alternate fins being struck up into the channel of the fin element. The vertically arranged side walls of channels are provided with shoulders so that the fin elements can be stacked within each other. These stacks are fixed to the opposed surfaces of adjacent conduits in a heat exchanger. One disadvantage of the fin elements described is that the presence of the vertically arranged side walls of the channel-like fin elements requires a substantial amount of metal which is largely surplus to the requirements of good heat transfer, so that the fin elements are costlier than is desirable.
The stacks disclosed in U.S. Pat. No. 2,703,226 further result in double vertical side walls, which adversely affects heat transfer.
An object of the present invention is to provide an improved heat exchanger which reduces or overcomes the disadvantages mentioned above.